A drogue and a sea anchor are 2 totally different things and would be dangerous to use interchangeably unless it is capable of some magic metamorphosis....

Actually that is not far from the way it is supposed to work. Here is an article that describes how the variable drag design works. While sailing and using it as a droque, it is perfect, it doesn't spin or break the surface, but I have never tried to deploy one as a sea anchor, so you may be right. It is SOLAS approved as a 'compliant sea anchor' which is why a number of offshore racers and cruisers carry them I'm sure.

Since I try to avoid extreme conditions in my current boat, my primary interest is for an emergency steering device and drogue, but I have yet to use it for anything on Boomarang. I hope I never have to. I will rig it to see how effective it is though, just to know what I can expect if the time ever arises. Besides, if I ever need a tow, I might be better prepared there too.

drogues are designed to slow your advance underway...in other words keep you straight or from broaching while you make way...they are deployed from the stern

sea anchors are designed to "anchor" you in one spot....not underway in any shape or form....usually deployed from the bow so the boat can stand the pummeling of the seas.

marketing has blurred these simple definitions for decades....

while variable drag has some merit....when I need to stay off a lee shore...I'm not sure that's ever gonna do the job of a 15-20 foot diameter para...and it sure looks like it would provide too much drag for my vessels cleats so I would have to install a heavy duty attachment point....

then again...I'm better off spending on a great liferaft as my trawler couldn't survive in conditions that would need either....

A sea anchor is very useful if you lose power in even relatively mild sea conditions. Imagine getting some air in your fuel, and having to bleed the injectors while the boat is beam to the seas. Most people would barf all over the ER in those conditions. Even waiting for a tow can be a lot less miserable if everybody's not sick.

A drogue is useful if you lose steering. Fortunately that's only happened to me on small outboards, long ago. A makeshift drogue worked pretty well in those cases, while we worked on fixing the steering. As kids, the thought of stopping for repairs never occurred to us.